Adding Honeywell Outdoor Reset Module to Aquastat

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Old 09-03-14, 08:31 AM
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Adding Honeywell Outdoor Reset Module to Aquastat

Hello, first time post...

I tried Buderus and Honeywell and no one will help out as I am just a home owner. I was hoping someone could point out the best settings. My HVAC contractor wants $750 to add this $150 part (I ordered it yesterday online). So I will just do it myself. Buderus said the contractor (my oil company) that switched my system to LL 140F did me no favors. I have worked on HVAC systems in the past so this is not very hard, just need guidance on the settings. I will also change the LL to OFF to switch back to a Cold Start system.

Any help would be appriciated...


This system is installed in NH in a house constructed in 2006. The house is about 3600 sq/ft with 4 full baths and one half bath. It is a secondary residence and used 3-4 weeks during the summer and every other weekend throughout the year. We generally keep the house at 52F during the winter when we are away. For the past 9 years we have used approximately 1000 gallons of fuel per year.

Last year our service company installed a Honeywell Aquastat L7224U1002 and converted the boiler from a Cold Start to a Low Limit set point of 140F. They indicated the system would run better but I do not believe it is running any different (maybe just cleaner). In general the system has been running fine with the exception of using a lot of fuel (relative to the fact the house temp is usually 52F).

System hardware
- Buderus G215-5 Boiler
- Beckett CF375 Burner
- SWG Power Vent
- Field Controls Combustion Air System (CAS-3)
- Taco SR506 6 zone relay (each zone has its own Circulator)
o Zone: SuperStore Ultra SSU-80 (80 gallons) Hot water Storage Tank (set to 130F when home and 100F when away)
o Zone: basement Heat Controller (AHB1348-0A, 4 ton)
o Zone: attic Heat Controller (AHB1330-0A, 2.5 ton)
o Zone: attic Heat Controller (AHB1324-0A, 1.5 ton)
o Zone: attic Heat Controller (AHB1324-0A, 1.5 ton)
- Honeywell Boiler Electronic Aquastat (L7224U1002)
o Current settings (HL 190F, Hdf 10F, LL 140F, Ldf 10F, duu OFF, ASC 0 sec, bSP 190F, dhc NO)

I am adding a Honeywell Outdoor Reset Module (W8735S1000) and would like to know the recommended settings for it and the L7224. I believe I need to know the additional setting (otL, otH, btL, bP, bS, UUS) once I add the Outdoor Reset. I would also like to change the LL to OFF to switch the boiler back to Cold Start. In general also your comments on the current L7224 settings would be appreciated.
 
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Old 09-03-14, 09:03 AM
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This system is installed in NH in a house constructed in 2006. The house is about 3600 sq/ft with 4 full baths and one half bath. It is a secondary residence and used 3-4 weeks during the summer and every other weekend throughout the year. We generally keep the house at 52F during the winter when we are away. For the past 9 years we have used approximately 1000 gallons of fuel per year.
Your oil company simply made their pockets deeper by converting it to a warm start boiler, totally unnecessary. Being the home is only used every other weekend during the winter and you're keeping it at 52 degrees when unoccupied, personally I don't think you're going to see savings with the outdoor reset. You can manually turn down the high limit when you're away to something like 150 and probably have no problem maintaining 52 deg. in the home. Then turn it back up to 170 or 180 when the home is occupied. 190 is on the hot side and isn't doing you any good with fuel consumption either. Why is it set so high?
 
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Old 09-03-14, 10:54 AM
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All the settings for the L7224U1002 I listed were set by the oil company tech. I just wrote them down as I read them off the Aquastat. When I commented about the fuel usage to the tech when he was doing the yearly boiler/burner cleanout last week he suggested the Outdoor Reset and said it would be $750 installed. Later when I checked the price online and how simple it was to add I just ordered myself and will put on this weekend.

As for setting the Aquastat HL value when we come/go I am sure I will forget at some point so I would rather not have another procedure. Also there are times when others go to the house when I am not around and they could not perform this process.

I am open to changing any of the values and also thought the HL should be 180F and the LL should be OFF (not 140F).
 
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Old 09-03-14, 10:59 AM
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I forgot to mention but you could also infer from my initial description. The system has anti-freeze in it as the attic air handlers are in unheated space. Also the piping is all PEX.
 
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Old 09-03-14, 04:11 PM
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Another point, your hydronic hot air heat might not work well with an outdoor reset. I believe they are geared more towards radiant heat sources. Some of the pros might correct me if I'm wrong.

My .02 - Bring the boiler temp down to 160-170 set low to off and call it a day.
 
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Old 09-03-14, 04:58 PM
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Hi Doug, welcome...

ABSOLUTELY turn OFF the LL ! that tech screwed you on that.

I think I'm on Tom's team on this.

That five section buderus may be oversized for starters, but it does sound like a larger home from your description of the zones. How many BTUH is that monster?

You have FOUR heating zones, and one for the water heater for a total of FIVE zones, correct?

I presume based on the size of the AH's that the 'basement' unit is heating the first floor, living, dining, kitchen, etc... and the other three are heating bedrooms on a second floor?

What is the total sq ft of the home?

Air handlers (Hydro-Air heating) don't do well at all with water below say 140-145 and even that is a tad on the low side. Any cooler water than that and the exiting air feels cold. It IS warm, but it FEELS cold... drafty...

So you want the water to be at least say 150F entering. This probably means that the water coming OUT and heading back to the boiler will be around 130F or a bit cooler... and that's troublesome for a conventional NON-CONDENSING boiler.

We can't be there to evaluate the system, but your tech MIGHT have had some solid reasoning for setting the LL to ON... the return water from the AH's MIGHT have been too cool and causing flue gas condensation inside the boiler... this is corrosive and damaging to the boiler, flue pipe, and chimney. He might have set that to try and combat the condensation and as you say to keep the boiler cleaner.

In addition to turning OFF the LL, I would INCREASE the HDF to 20F.

I forget what the BSP setting is for? Can you refresh my memory?
 
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Old 09-03-14, 07:39 PM
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Outdoor resets and air handlers do not mix. End of story. No need for a low limit. The 215 is a good boiler but seems like a waste with a beckett burner. I never understood why companies did this.
 
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Old 09-04-14, 05:59 AM
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Thanks everyone for your input...

NJ Trooper...
The house is 3600 sq/ft above ground. With another 1200 or so in the basement that is also heated. Four heating zones and one zone for hot water. The basement air handler has one zone damper with the first floor one zone and the basement the other zone. The boiler ran fine for 7-8 years with no LL. bSP is the boiler Set-Point which is only shown on the L7224 when the Outdoor reset is installed. I am not sure it is just displayed or it is actually a value that can be set.

Dburr9
What you state relative to the Outdoor Reset on a hydro system seems to be the consensus, thanks. Just out of curiosity what burner would you use on the system? I do not know much about burners but thought the Beckett was ok?

So I think this is my plan. I will not install the Outdoor Reset. I will set the LL to OFF, HL to 180F, and HdF to 20.
 
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Old 09-04-14, 07:53 AM
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That's a large home, your boiler may be close to correctly sized.

There's nothing wrong with Beckett burners... just some people have negative opinions about them, and on the other hand there are as many or more positive opinions. Some ppl don't like Riello, some like chocolate ice cream, some like vanilla.

Nothing but opinions and likes / dislikes for whatever reason. Take all opinions with the proper number of grains of salt.
 
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Old 09-04-14, 01:56 PM
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I love Becket burners. Especially on those midnight no heat calls. However, Buderus boilers should have a riello. That's my opinion. I don't like changing parts on a riello because it's a nightmare. Granted I've only had to change a motor twice in my career. When I say I like beckets, it's mostly because every part is really easy to change. I could disassemble and rebuild a Becket with new parts in about 10 minutes. It takes me a half hour just to change a riello motor. All in all it doesn't matter. A burner is a burner. They all do the same thing.
 
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